Transcutaneous Electrical Nerve Stimulation (TENS) has been an accepted mode of electrotherapy for many years and is well characterized (Kahn, J., Principles and Practice of Electrotherapy, New York, Churchill Livingstone, 1987; Greene, R. W. et al., Transcutaneous Pain Control and/or Muscle Stimulating Apparatus, U.S. Pat. No. 4,147,171). TENS is primarily intended for pain relief via a nerve signal blocking mechanism, but it has also been used to promote healing. TENS devices typically deliver biphasic stimulus pulses between 10 milliamperes (mA) and 100 mA in amplitude. Pulse amplitude, pulse width and pulse rate are often user adjustable. The stimulus pulse is delivered to a pair of electrodes that are manually placed over major muscle groups or nerves that are to receive the stimulation. There are several portable TENS devices available for clinical use (e.g., TENZCARE, 3M Co., St. Paul, Minn.; Premier TENS, American Imex, Irvine, Calif.; ProTENS, NTRON, Sugarland, Tex.).
Microcurrent electrotherapy, sometimes abbreviated as "MENS" (Microcurrent Electrical Neuromuscular Stimulation), is becoming a more widely accepted clinical practice for decreasing or eliminating pain and stimulating the healing process. MENS is typically used for pain relief and, more typically, for tissue healing by affecting the injured tissue at the cellular level. Tissues that respond to MENS include muscle, tendon, bone, nerve and skin. The effectiveness and use of microcurrent electrotherapy has been well documented (Wallace, L., P. T., MENS Therapy: Clinical Perspectives, Vol. 1, Cleveland, privately published, 1990; Picker, R. I., M.D., Microcurrent Therapy: Harnessing the Healing Power of Bioelectricity, (publication pending); Kahn, J., Principles and Practice of Electrotherapy, New York, Churchill Livingstone, 1987; Snyder-Mackler, L. and Robinson, A., Clinical Electrophysiology, Baltimore, Williams & Wilkins, 1989). However, the exact mechanisms by which microcurrent electrotherapy provides these benefits have yet to be completely characterized. MENS devices deliver a much smaller current than TENS devices (typically 20 uA (microamperes) to 600 uA). The waveforms used are typically a positive direct current (DC), negative DC or a combination of these in which the polarity is switched at an adjustable rate (usually 0.3 Hz to 30 Hz using a 50% duty cycle waveform). The use of microamperes of electrical current in MENS therapy, as opposed to TENS therapy, results in little or no patient discomfort or even sensation during application. As with TENS, electrodes must be manually placed over the tissue that is to receive the stimulation. Electrode pads are placed to follow an electrical pathway within the body, e.g., from the origin to the insertion of a muscle following muscular electrical flow, down the pathway of radiating nerve pain, through acupuncture or trigger points, or medial/lateral through a swollen joint. Sometimes electrodes are implanted into the tissue. There are currently several portable microcurrent units (a.k.a. microcurrent stimulators) available for clinical use (e.g., MENS 2000 stimulator, MONAD Corp., Pomona, Calif; PicoPulse, NAPCOR, Rancho Cucamonga, Calif.). Common user controls include amplitude (intensity), polarity and frequency.
Iontophoresis is the use of DC (as opposed to alternating or pulsed electrical currents used in microcurrent stimulators and TENS devices) to drive a charged drug into injured tissues to relieve pain and promote healing (see prior references and Nelson, R. and Currier, D., Clinical Electrotherapy, East Norwalk, N.J., Appleton-Century-Crofts, 1987). Iontophoresis has been shown to be a very effective modality for pain relief and tissue healing when used with appropriate pharmacologic agents (e.g., lidocaine, corticosteroids, etc.) and has been reported to affect edema by moving ions and larger, charged molecules in the blood and tissues which causes a subsequent movement of fluid. Larger currents (up to 5 milliamperes DC) are useful for fast, short-term effects, whereas smaller currents (in the hundreds of microamperes DC) are more useful for longer-term effects. As with TENS and MENS, electrodes must be manually placed over the site that is to receive the drug. However, the electrode (or skin site) must be coated with a gel or other material that holds the drug to be delivered. There are a number of commercially available, portable devices used for iontophoresis (e.g., MicroPhor and IontoPhor, Life-Tech, Inc., Houston, Tex.; TransQ and TransQ2, IOMED, Inc., Salt Lake City, Utah). User controls typically include intensity and polarity.
Current electrotherapy units have a number of characteristics that limit their functionality as an electrotherapy tool. There are several problems associated with the electrodes that are typically used. Electrodes generally require adherence to the skin with tape or an adhesive-conducting material. The tape or material often becomes loose over time rendering the electrodes and therapy ineffective. This is especially true in active patients in which the activity (e.g., passive range of motion, light exercise, normal daily activities) is prescribed as part of the overall rehabilitation therapy plan. Skin irritation may also occur with the use of these electrodes as a result of reactions to the adhesive materials used. Electrode placement is critical to effective treatment. However, patients often lack the anatomic knowledge needed to effectively place the electrodes by themselves which necessitates frequent clinic visits and limitations on therapeutic activities. The current units are about the size of a small personal radio (e.g., 3 inches wide, 4 inches long, 1 inch deep) with lead wires used to connect to the electrodes. The units are often worn on a patient's belt or in a large pocket. Problems associated with these units include: detachment of lead wires from the electrodes or stimulator during patient movements, e.g., therapeutic range of motion or exercise; interference of lead wires with daily activities; and reports of bulkiness that lead to decreased use of the stimulator unit.
Current units are also designed primarily for a single operational mode, i.e., TENS, MENS or iontophoresis. Many patients benefit from a combined therapy in which TENS, MENS and/or iontophoresis are used during different stages of therapy, which may also include the more standard interventions such as tissue compression, cold/hot treatment, passive range of motion, and exercise. The availability and use of different electrotherapy methods is often critical to treatment immediately post injury. Existing units do not promote this multi-faceted approach to injury management because they require separate devices to be available, typically with conflicting electrode requirements. Independent use of these units by a patient (per clinician instructions) as part of a complete treatment plan of managed self care is very difficult because of all the problems noted above. As such, the current units do not promote the current trend in the health care field toward managed self care.
Accordingly, there exists a need for a miniaturized, portable electrotherapy device capable of delivering multiple modes of operation, specifically TENS, MENS and iontophoresis, to an injured joint in the body for the purpose of treatment and therapy for a variety of injury-related conditions. The device must be unobtrusive and not require any parts to be adhered to the skin. It must promote proper electrode placement while being comfortable enough to be worn on the body during everyday activities. It must permit complete freedom of movement without fear that its parts will become loose or detached. The present invention fulfills these needs and provides further related advantages.